Even before the ownership of the unappropriated lands in the Northern Neck had been definitely determined, Lord Fairfax had made known his desire to open, to settle, and to develop them. As the first surveying party sent out for these purposes had experienced no mishaps or unusual adventures, young Washington was allowed to accompany the party going beyond the mountains in the spring of 1748. This party was in charge of James Genn, the county surveyor of Prince William County and a man of many adventures in the wilderness. Accompanied by young Washington, rodmen, chainmen, and other attendants, Genn set out March 11. Going by way of Ashby's Gap and Greenway Court he made his first important stop on the South Branch of the Potomac where that stream intersected the "Fairfax Boundary" which had been determined two years previously. [George] Washington kept a diary of his experiences and adventures.

↑James-3 Genn (James-2, James-1 ) was born 27 August 1718. On 19 December 1739 he sold the land in Northumberland County that he had inherited from his father and moved to Prince William County. He purchased 400 acres in Hamilton Parish on 29 April 1740 and lived there with his wife Hannah. On 21 August 1746 he purchased 110 acres on Falmouth Road and Walnut Branch and on 21 May 1748 he purchased an additional 150 acres adjacent to the 400 acres acquired in 1740. Between 1746 and 1748 he was granted five blocks of land in Prince William and Orange counties by Right Honorable Thomas Lord Fairfax, a total of 1415 acres.